RU2550704C1 - Peat alkaline drilling mud for well drilling in permafrost rocks - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: peat alkaline drilling mud for well drilling in permafrost includes, wt %: peat 5-7; potassium-containing alkaline modifier 0.5-1.5; potassium chloride as inhibitor 1-3; polymer flocculant and fluid loss reducing agent Polydia 0.1-0.5; froth suppressor MAC-200M 1-3; the rest is water.

EFFECT: enhanced reliability of well drilling in clay rocks, especially in permafrost under abnormally low reservoir pressure due to high inhibition properties of drilling mud and low foaming.

2 tbl, 1 dwg

Description

The invention relates to the oil and gas industry, namely to drilling wells in permafrost (MMP), especially in conditions of abnormally low reservoir pressure (AAP).

In the process of drilling wells, various complications are often observed. Despite the accumulated experience of drilling wells in various geological conditions, the time spent on dealing with complications during well drilling remains significant (up to 7-10%), due to the complication of drilling conditions and an increase in the number of deviated and horizontal wells. More than 50% of the emergency time is spent on eliminating the complications associated with rock instability during drilling. Complications arising from this are more difficult to predict and prevent without the use of physico-chemical methods of interaction of the flushing fluid with the rock [Basarygin Yu.M. et al. Complications and accidents during the drilling of oil and gas wells: Textbook for universities. - M .: Nedra LLC, 2000. - 680 p.], [Wafin P.M. et al. The choice of drilling fluid for drilling wells in complicated mining and geological conditions // Oil industry. 2013. No1. - S. .53-55].

Scree and collapse of the walls of the wells, mainly occur during the passage of compacted clays, mudstones or shales. This is due to the fact that during the drilling process they are moistened with mud filtrate, which ultimately reduces the tensile strength of these rocks. Rockfalls are most often caused by rock swelling. Penetration of free water, which is contained in large quantities in drilling fluids, into horizons composed of clay rocks, leads to their swelling, bulging into the wellbore and, ultimately, to collapse on the bottom.

In the design and construction of production or exploratory wells, they tend to take into account the influence of clay swelling on the course and results of drilling. In this case, it is important to have in advance the data of direct experimental estimates of the swelling of the samples of drillable rock in the environments of the proposed drilling fluids.

Peat, which is a sediment of organic origin, is an environmentally friendly material, cheap enough, very affordable, and at the same time has the properties that make it possible to obtain high-quality drilling fluids with minimal costs of chemicals from among the least toxic, i.e. It is a worthy substitute for traditionally used clay materials.

Peat drilling fluids are environmentally friendly, easily cleaned of sludge, and after use they can be used for the remediation of disturbed lands both in the form of fluids and formed unused peat residues in wells.

Peat contains a whole complex of substances that are very valuable from the point of view of drilling fluids. These are humic acid, hemicellulose, starch and pectin, bitumen, lignin, etc. Humate reagents from peat are already used to control the properties of drilling fluids due to their availability, low cost of raw materials and ease of preparation.

Known clay-free drilling fluids prepared by treating an aqueous peat suspension with alkaline agents, which are used as hydroxides, carbonates, silicates of alkali metals [Drilling fluids for difficult conditions / O.K. Angelopulo, V.M. Podgornov, V.E. Avakov - M .: Nedra, 1988].

The disadvantage of three-component solutions (peat-water-alkaline reagent) is the high filtration and low processability of the resulting system. The use of such solutions is limited to the intervals composed of loose absorbing rocks.

A well-known drilling fluid in which a peat-alkaline suspension, in order to reduce viscosity, static shear stress in conditions of polymineral aggression, contains the following ingredients (% wt.): Humate-containing substance - 4-8; alkaline electrolyte - 0.2-1.5; gelling agent - 1-3; organic stabilizer - 0.1-1; inhibitor - 1-4 and water - the rest [A.S. USSR N 945163, class C09K 7/02, publ. 07/23/82 g].

The disadvantage of this solution is the low flocculating ability and, despite the presence of an inhibitor in the composition, unsatisfactory inhibitory properties when used for drilling drilling intervals composed of clay rocks. The consequence of these disadvantages is a violation of the stability of the wellbore, the enrichment of the drilling fluid with particles of sludge, including fine ones, which ultimately leads to a change in structural and mechanical parameters.

A well-known drilling fluid containing peat alkaline reagent, polyacrylamide (PAA), a water-soluble metasilicate, a surfactant and water, in which sulfanol or OP-10 is used as a surfactant to reduce structural viscosity [RF Patent No. 2041907, cl. C09K 7/02, Andreson B.A., Abdrakhmanov R.G., Bochkarev G.P., Sharipov A.U., Rekin A.S., Labazov A.V., 1995].

The disadvantage of the solution is the high foaming during cooking, which reduces the specific gravity of the solution.

The closest technical solution selected for the prototype is a clay-free drilling fluid containing peat, an alkaline modifier, an inhibitor, a flocculant and water. Potassium-containing alkaline reagent is used as an alkaline modifier, potassium chloride is used as an inhibitor, polyacrylamide (PAA) is used as a flocculant in the following ratio of components,% wt .: peat - 5-7; potassium alkaline modifier 0.5-1.5; potassium chloride 1-3; PAA - 0.002-0.004; water - the rest [RF Patent No. 2102429, cl. C09K 7/02, Anisimov A.A .; Vorobyova N.M .; Avdeeva N.D .; Demidova O.V .; Zakharov B.I. Research and Design Institute "SeverNIPIgaz", 1998].

The disadvantage of the prototype is the high foaming. Despite the presence of an inhibitor and PAA in the composition, unsatisfactory inhibitory properties are observed when using this solution for drilling clay-bedded intervals, especially in the areas of permafrost with anticorrosive pressure.

The challenge facing the creation of the invention is to increase the reliability of drilling wells in rocks, composed of clay, especially in the areas of permafrost during an API.

Achievable technical result, which is obtained as a result of the invention, consists in the development of peat-alkaline drilling mud with high inhibitory properties in relation to clay rocks and low foaming.

The task and technical result are achieved by the fact that in the well-known peat-alkaline drilling fluid for drilling in permafrost rocks, including peat, an alkaline modifier, inhibitor, flocculant and water, in contrast to the prototype, it additionally contains a water loss reducer and antifoam, and as a water loss reducer Polydia polymer is used, and MAC-200M as an antifoam, with the following ratio of components,% wt .: peat - 5-7; potassium alkaline modifier 0.5-1.5; the inhibitor is potassium chloride 1-3; Polydia polymer flocculant and fluid loss reducer - 0.1-0.5; antifoam MAS-200M - 1-3; water is the rest.

A comparative analysis with the prototype allows us to conclude that the inventive peat-alkaline drilling fluid for drilling in permafrost rocks differs from the known one in that it additionally contains an antifoam, and Polydia polymer is used as a flocculant and water loss reducer, and MAC-200M as an antifoam.

Polydia polymer used as a fluid loss reducer is a block of modified low molecular weight polyacrylamide with a low anionic charge density from white to cream. Designed for use in technological operations to increase oil recovery, leveling the injectivity profile of injection wells, to modify the permeability of the pore reservoir. It is made according to TU.

Polydia Polymer Quality Indicators

Flocculant is a reagent necessary for stabilization of water-swellable and dispersible clays.

The flocculant acts on the particles of the solid phase without changing the electrical properties, forming bridges of polymer macromolecules between the particles of the solid phase due to adsorption forces.

A flocculant is in most cases water-soluble polymers with a large molecular weight, having an anionic, cationic or neutral charge of both natural and artificial origin. Not all polymers can be effective flocculants. This depends on the chemical composition of the macromolecules, the presence and number of ionogenic groups in it, the activity of which even depends on the structure and electric charge of the surface of the particles of the flocculated solid phase. With a certain combination of these and other factors, fairly strong bridging bonds between the polymer and solid particles can occur, forming joint agglomerates. An indispensable condition for flocculation is the possibility of adsorption of already fixed macromolecules on the free surface of other particles.

The MAC-200M product is used for processing drilling fluids. Physico-chemical properties allow it to be used as an antifoam in aqueous solutions and as a stabilizer for carbohydrate-based solutions. The antifoam is not soluble in aqueous and carbohydrate environments, preserves technological properties in the temperature range from 40 to 250 ° C.

The mechanism of defoaming in clay suspensions is based on the effect of attaching the air globules to the hydrophobic part of the reagent, promoting their coalescence, enlargement and flotation to the surface. After the destruction of air bubbles on the surface, a particle of antifoam, without losing activity, is again included in the work. Repeated use of each particle causes minor reagent losses.

Directly in the field, when performing drilling operations based on the MAS-200M powder reagent, it is possible to prepare antifoam for drilling fluids, waterproof lubricants, detergents for degreasing machine parts and mechanisms, and to purify water from oil products. It is also advisable to use this reagent for defoaming in the production processes of the pulp and paper industry and in the technology for treating industrial wastewater in the oil refining industry.

The invention meets the criterion of "inventive step", since the combination and ratio of components in the inventive clayless drilling mud is not obvious to a person skilled in the art.

To evaluate the effectiveness of the developed peat-alkaline drilling fluid compositions, a series of experiments was carried out to determine the swelling index of clay briquettes in the environments of the studied fluids. The experimental work was carried out on a OFITE longitudinal swelling plant for clay briquettes.

The OFITE device is designed to study the interaction between drilling drilling fluids in motion and samples of inorganic rocks containing chemically active clays under specified reservoir conditions. The measured swelling characteristics are used to evaluate and eliminate frequently encountered problems when drilling wells composed of clay rocks.

When preparing solutions, the following chemicals were used:

- Peat is an organic dispersed phase.

- KOH - potassium alkaline modifier.

- KCl - clay swelling inhibitor - potassium chloride.

- Polydia (an analogue of CMC) - Polydia polymer is a flocculant and solution loss reducer.

- Defoamer MAS-200M.

The compositions of the studied solutions are presented in table 1.

The potassium-containing reagent serves to modify the peat builder. Under this condition, saponification of peat particles and enrichment of the aqueous phase of a clay-free solution with potassium ions occur simultaneously.

Additional enrichment of the peat solution with potassium ions occurs with the introduction of potassium chloride.

The combination of a potassium-containing alkaline modifier with potassium chloride leads to the enrichment of the filtrate of peat drilling mud with potassium ions, which actively contribute to suppressing the process of swelling and hydration of clay rocks.

For the manufacture of briquettes was used bentonite clay powder Zyryanovskogo deposits of the Kurgan region. Samples weighing 15 g were placed in a high-pressure compactor, where samples for studies were prepared under pressure of 6000 psi (~ 41.3 MPa) and for 30 min.

After preparation, the samples were placed in special cylinders into which the studied compounds were introduced and kept for 4 hours.

The test results of the solutions of the prototype and the proposed compositions are presented in FIG.

Analyzing the results, it can be stated that the developed solutions 2, 3 and 4 showed high inhibitory properties compared with solution 1, taken as a prototype.

However, the drawback of solution 2 is its increased conditional viscosity of 2100 s. In our opinion, the composition of such a solution can be recommended in the future as a viscoelastic composition (WCS) for killing oil wells.

The nominal viscosity of solutions 3 and 4 is 114 s and 30 s, respectively. Thus, analyzing the obtained results and research findings, when drilling oil and gas wells in the intervals composed of clay rocks, it is possible to recommend a clay-free drilling fluid containing peat, an alkaline modifier, an inhibitor, an antifoam, Polydia polymer and water.

The inventive solution provides an increase in inhibitory properties and has low foaming properties, which allows it to be used when drilling wells in rocks composed of clay rocks, especially in the areas of permafrost with anticorrosive pressure.

Claims (1)

Peat-alkaline clay-free drilling fluid for drilling in permafrost, including peat, a potassium-containing alkaline modifier, an inhibitor is potassium chloride, a fluid loss reducer is a polymer flocculant and water, characterized in that it additionally contains MAC-200M antifoam, and a water loss polymer reducer , in the following ratio of components,% wt .:
peat 5-7 potassium alkaline modifier 0.5-1.5 potassium chloride 1-3 Polydia polymer 0.1-0.5 antifoam MAS-200M 1-3 water rest

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